1. Field of the Invention
The present invention relates to an optical reception device of a remote controller, and more particularly, to an optical reception device of a remote controller, where the optical signal reception efficiency is improved by adopting a refractive index distribution lens.
2. Description of the Related Art
Generally, remote control systems for remotely controlling televisions, videocassette recorders, compact disc players and other household electronic products are composed of a transmission device in the remote controller itself, for emitting an optical signal (mainly, an infrared signal) and a reception device in the apparatus to be controlled, for receiving the optical signal transmitted across a space from the transmission device.
FIG. 1 is a schematic cross-sectional view of a conventional remote controller reception device. The remote controller reception device comprises an optical reception window 101 to which the optical signal is incident, an optical transfer guide 102 having a cylindrical shape for transferring the optical signal passed through optical reception window 101 and an optical sensor 103 for sensing an optical signal transferred via optical transfer guide 102. The optical signal incident via optical reception window 101 travels along the longitudinal axis of optical transfer guide 102 while being reflected on the inner wall of optical transfer guide 102 to reach an optical sensor 103. An incident angle is defined when an optical signal is incident to optical reception window 101.
In the conventional remote controller reception device shown in FIG. 1, there is no problem when the incident angle is small. However, when the incident angle is large, i.e., the remote controller transmission device and the optical reception window of the remote controller reception device are grossly unparallel, multiple reflections occur on the inner wall of optical transfer guide 102, so that the signal is weakened and the reception efficiency of the optical sensor is reduced. Also, when the optical signal is incident on the optical sensor at a large incident angle, the sensitivity of the optical sensor is reduced so that the remote control function cannot be performed reliably.
FIG. 2 shows an improved .optical reception device for overcoming the above-describe problems, where the optical: reception window of the remote controller reception device shown in FIG. 1 has a convex lens 201 so that the optical signal can be more exactly focused on the center of optical sensor 203. As a characteristic of convex lens, the optical signal is refracted to reach a position comparatively far from the convex lens, of the inner walls of optical transfer guide 202, even when the incident angle of optical signal is large. As a result, the occurrence of multiple reflections on the inner walls of optical transfer guide 202 is slightly restricted, so that the reception efficiency of the optical signal is increased compared with the remote controller reception device shown in FIG. 1.
However, in the case of the remote controller reception devices shown in FIGS. 1 and 2, since the occurrence of multiple reflections in the inner wall of optical transfer guide cannot be overcome, the transfer efficiency of the optical signal is inherently reduced.